1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, a process cartridge and an electrophotographic apparatus. More particularly, it relates to an electrophotographic photosensitive member containing a specific resin, a process cartridge and an electrophotographic apparatus which have such an electrophotographic photosensitive member.
2. Related Background Art
Electrophotography makes use of a photoconductive material comprised of a support coated with a substance that changes in electrical resistance in accordance with the amount of irradiation received during exposure and also has insulating properties in the dark as disclosed in U.S. Pat. No. 2,297,691. Fundamental features required in electrophotographic photosensitive members making use of such a photoconductive material are (1) that the electrophotographic photosensitive member is chargeable to a suitable potential in the dark, (2) that it may less scatter and lose the potential in the dark and (3) that it releases electric charges quickly upon irradiation by light.
As electrophotographic photosensitive members, inorganic photosensitive members, having a photosensitive layer composed chiefly of an inorganic photoconductive compound, such as zinc oxide or cadmium sulfide, have conventionally been in wide use. These fulfill the above conditions (1) to (3), but have not necessarily been satisfactory with respect to thermal stability moisture resistance, durability and productivity.
In recent years, in order to overcome disadvantages of such inorganic photosensitive members, electrophotographic photosensitive members composed chiefly of organic photoconductive compounds have been energetically studied and developed. For example, a photosensitive member having a charge transport layer containing a triallylpyrazoline, as disclosed in U.S. Pat. No. 3,837,851, and a photosensitive member comprised of a charge generation layer formed of a derivative of a perylene pigment and a charge transport layer formed of a condensate of 3-propylene with formaldehyde, as disclosed in U.S. Pat. No. 3,871,880, are known in the art.
In addition, some of the organic photoconductive compounds enable free selection of photosensitive wavelength regions of electrophotographic photosensitive members. For example, as azo pigments, Japanese Patent Application Laid-open No. 61-272754 and No. 56-167759 disclose substances showing a high sensitivity in the visible region. Also, Japanese Patent Application Laid-Open No. 57-19576 and No. 61-228453 disclose compounds having a high sensitivity up to the infrared region.
Of these materials, those showing a sensitivity in the infrared region are used in laser printers (hereinafter xe2x80x9cLBPxe2x80x9d) and LED printers having made remarkable progress in recent years, and have become in great demand.
Electrophotographic photosensitive members making use of these organic photoconductive compounds are often used as function-separated photosensitive members having a charge generation layer and a charge transport layer formed superposingly, in order to satisfy both electrical and mechanical properties.
Meanwhile, as a matter of course, electrophotographic photosensitive members are required to have sensitivity, electrical properties and optical properties which have been adapted to the electrophotographic processes employed.
In particular, in the case of electrophotographic photosensitive members used repeatedly, the electrical and mechanical external force produced by corona or contact charging, exposure, development with toner, transfer, and surface cleaning is directly applied to the surfaces of the electrophotographic photosensitive members. Hence, they are required to have durability to such an external force.
Stated specifically, they are required to have durability to electrical deterioration caused by ozone and nitrogen oxides at the time of charging and to mechanical deterioration and electrical deterioration such that the surface is worn or scratched as a result of its friction with a cleaning member.
With regard to the electrical deterioration, there is a phenomenon in which carriers stagnate at areas irradiated by light to cause a potential difference between those areas and areas not irradiated by light. This phenomenon occurs as a photomemory.
With regard to the mechanical deterioration, the organic photosensitive members, mostly made of soft materials, have an inferior durability in mechanical deterioration different from inorganic photosensitive members. Hence, the former is especially earnestly sought to be improved in durability.
A variety of attempts have been made in order to satisfy such durability characteristics required in photosensitive members.
As resins widely used in surface layers and having good wearability and electrical properties, a polycarbonate resin having the skeleton formed of bisphenol A attracts notice, but it does not solve all the problems stated. It has the following problems:
(1) It has so poor a solubility as to show a good solubility only in some halogenated aliphatic hydrocarbons, such as dichloromethane and 1,2-dichloroethane. Moreover, since these solvents have a low boiling point, coated surfaces tend to whiten when photosensitive members are produced by the use of coating fluids prepared using such solvents. Solid-matter management of coating fluids also takes much time.
(2) It is partly soluble in solvents other than the halogenated aliphatic hydrocarbons, e.g., in tetrahydrofuran, dioxane and cyclohexanone or mixed solvents of any of these. However, the resultant solutions have poor properties with time, e.g., they gel in few days, and are not suited for the production of photosensitive members.
(3) Moreover, even if the problems (1) and (2) are solved, the polycarbonate resin having the skeleton formed of bisphenol A tends to cause solvent cracking.
(4) In addition, in the case of conventional polycarbonate resins, coating films formed of such resins have no lubricity, and hence photosensitive members tend to be scratched to cause in some cases i) faulty images under cleaning conditions so set that the electrophotographic photosensitive member may wear in a low quantity or ii) faulty cleaning or toner melt-adhesion due to premature deterioration of a cleaning blade.
The problem on the solution stability referred to in paragraphs (1) and (2) has been solved by using a polycarbonate-Z resin having a bulky cyclohexylene group as a polymer structural unit, or by copolymerization with bisphenol Z or bisphenol C.
The problem of solvent cracking can be solved by using a silicon-modified polycarbonate or an ether-modified polycarbonate as disclosed in Japanese Patent Application Laid-Open No. 6-51544 and No. 6-75415. However, compared with conventional polycarbonate resins, these modified polycarbonates take a structure that imparts a flexibility to internal stress in a polymer as a countermeasure to solvent cracking, and hence have the disadvantage that the polymer itself has a low mechanical strength.
In addition, recently, a contact charging system is becoming prevalent in which a voltage is directly applied to a charging member to apply electric charges to an electrophotographic photosensitive member as disclosed in Japanese Patent Application Laid-Open No. 57-17826 and No. 58-40566. This is a method in which a roller type charging member constituted of a conductive rubber or the like is brought into direct contact with the electrophotographic photosensitive member to which electric charges are applied. This method has advantages such that ozone is generated in a greatly smaller quantity than Scorotron or the like and, while in Scorotron about 80% of the electric currents flowing in a charging assembly are wasted since they flow to a shield, the contact charging member is free from such waste and is very economical.
However, the contact charging has the disadvantage that its charging stability is very poor because of discharging due to Paschen""s law. As a countermeasure to this disadvantage, what is called an AD/DC charging system is devised in which an alternating-current voltage is superimposed on a direct-current voltage (Japanese Patent Application Laid-Open No. 63-149668).
This charging system has brought about an improvement in stability at the time of charging, but has anew caused the disadvantage that the electrophotographic photosensitive member is abraded in a large quantity because the discharge quantity on the surface of the electrophotographic photosensitive member is large. Thus, it has come to be required that not only mechanical strength, but also electrical strength is ensured.
An object of the present invention is to provide an electrophotographic photosensitive member that has solved the problems caused when conventional polycarbonate resins are used in surface layers, has a high mechanical strength while having solvent cracking resistance and also resists any electrical deterioration due to a contact charging member, and a process cartridge and an electrophotographic apparatus that have such an electrophotographic photosensitive member.
The present invention provides an electrophotographic photosensitive member comprising a support and a photosensitive layer provided thereon;
a photosensitive layer fulfilling at least one condition of the following conditions (A) and (B):
(A) containing a polymerization product of a monomer having a reactive group represented by the following Formula (1):
xe2x80x94Oxe2x80x94(xe2x80x94CH2xe2x80x94)nxe2x80x94CHxe2x95x90CHxe2x80x94R0xe2x80x83xe2x80x83(1)
wherein R0 represents a hydrogen atom or a methyl group, and n represents O or 1, provided that Ro represents a methyl group when n is O; and
(B) containing a copolymerization product of a monomer having a reactive group represented by the following Formula (2):
xe2x80x94Oxe2x80x94CHxe2x95x90CH2xe2x80x83xe2x80x83(2)
with a charge-transporting material having a reactive group capable of reacting with the monomer.
The present invention also provides a process cartridge and an electrophotographic apparatus which have the electrophotographic photosensitive member described above.